Resonant switch system



Nov. 14, 1950 H. REIFEL ,5

RESONANT SWITCH SYSTEM Filed Aug. 14, 1946 CCTA CCTB CCTC CCTD F/GZ IN VEN TOR.

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Patented Nov. 14, 1950 UNITED TOFFICE RESONANTSWITCH SYSTEM Harry Reifel,;Waltham, Mass., assignor, by 'inesne assignments, to Stevens-Arnold Inc' /Boston, a Mass, a. corporation of Massachusetts Application'August 14, 1946, Serial No. 690,389

4-Olaims. 1

This invention relates: to electric switches having resonant armaturesxwhich close e'l'ectric circuits when.- alternating: currents having: the: frequencies to whichitheir-armatures areresonant, are. supplied through: their-energizing .coils; and

which. are known. generallyas resonant switches.

Resonant. switch systems: each having; plurality of switches resonant at difierentfrequ'encies, and energized from a variable frequency, electric current source, have been proposed for communications and other purposes. Disadvantages of such, systems .have been that the switches resonant at different frequencies have not. had the same sensitivity, and they have not operated efliciently.

This invention provides .a resonantxswitch system having aplurality .of switches resonant at different: frequencies, the energizing coil'si;being connected in series-with the secondary of a transformer having its primary connected to a variable frequency, electric current source.

A feature of the invention is-that the'switches resonant at the higherfrequencies have-more turns of wire in their energizing coils for maintaining the same sensitivity in all of the switches.

Another feature of the invention is that the contacts of the switches resonant at the higher frequencies, are more closely spaced for reducing the power required for maintaining the same sensitivity in all of the switches.

Another feature of the invention is that the transformer to the secondary of which, the energizing coils of the switches are connected, is a step-down transformer whereby the current through the coils is increased and their number of turns is reduced.

Another feature of the invention is that the coils of all of the switches of the system, have the same resistance whereby switches having different resonant frequencies can be substituted without changing the resistance of the system.

An object of the invention is to increase the efiiciency of resonant switch systems.

Another object of the invention is to maintain the same sensitivity in all of the switches in a resonant switch system.

Another object of the invention is to provide a resonant switch system adapted to receive a variety of switches resonant at different frequencies without loss in sensitivity or efficiency.

The invention will now be described with reference to the drawing, of which:

Fig. 1 is a circuit schematic illustrating a resonant switch system embodying this invention, and

Fig. 2 is a side elevation, in section, illustrating one form of resonant switch which maybe used in ture ['5 to strike the conta'c't 1'6 'closingcircuit A.

Likewise the armatures I'T, H3 and 2| of the switches I2, I3 and I 4 respectively, may be resonant at 200, 300 and 400' cycles per second, for example, and when a current of200 cyc'lesper second is applied tothe transformer primary,- the current through thecoil 8 will" cause the'armature I! to strike the contact I8 closing the circuit B. When a current having-a frequency of 300 cycles per second is applied to the 'transformer primary, the current through the coil 9 will cause the armature IE to strike the contact 20 closing the circuit C. When a current having a frequency of 400 cycles per second is applied to the transformer primary, the current through the coil l0 will cause the armature 2| to strike the contact 22 closing the circuit D.

Referring now to Fig. 2 which illustrates a preferred form of resonant switch which may be used, the reed armature 24 of magnetic metal is supported as a cantilever beam with one end between the metal block 25 and the base 26, and with its other end spaced from the contact strip 21 which is supported between the permanent magnet 28 and the insulating strip 29 which is held against the base 26. The channel extension lips 30 and 3| extend over the block 25 and the insulating strip 32 on the magnet 28 and hold the described assembly in position.

The cylindrical coil form 33 extends around the armature 24 and has wound thereon, the wire 34 forming the energizing coil of the switch. For different resonant frequencies, the armature 24 would have different lengths.

When alternating current having the frequency to which the armature 24 is resonant, is passed through the coil, the armature 24 is magnetized and is attracted to and repelled by the contact strip 21 which is magnetized by the magnet 28, and strikes the strip 21 closing a circuit in which the armature and the contact strip are connected.

More power is required for operating the switches that are resonant at the higher frequencies, and to maintain the same sensitivity in all the switches, the number of turns in the coil 8 of the switch I2 is larger than the number of turns in the coil 1 of the switch II; the number of turns in the coil 9 of the switch 13 is larger than the number of turns in the coil 8 of the switch 12, and the number of turns in the coil of the switch [4 is larger than the number of turns in the coil 9 of the switch [2.

The power required for operating the resonant switches when they have the same contact spacing, varies with the cube of the frequency towhich they are resonant. This power may be reduced by decreasing the contact gap, and acarmature is resonant, a second contacttouched by said second armature whenit is vibrated at its resonant-frequency; a first energizing winding cordingly for reducing the number of energizing coil turns for maintaining the same sensitivity in all of the switches; the spacing of the armature I! from the contact I8 is less than that between the armature l5 and the contact 16; the

spacing of the armature l9 from the contact, 20 is less than that between the armature I"! and the contact 18, and the spacing between the armature 2| andthe contact 22 is less than that between the armature l9 and thecontact 20.

The coils having fewer turns are wound with smaller diameter'wire whereby the resistance of all coils is the same. Thus switches having differentresonant frequencies can be substituted for other switches without changing the resistance of the system.- v E'or reducing the number of energizing coil turnsrequired, a step-down transformer is used for providing increased current.

A particular advantage of this invention is that different switches having difiercnt resonant frequencies can be. substituted for other switches havingother resonant frequencies without affecting the sensitivity or the efficiency of the system.

While one embodiment of the invention has been described for the purpose of illustration, it should be understood that the invention is not for said first armature, and a second energizing winding for'said second armature connected in series-with said first winding, said second winding having more turns than said first winding.

24A resonant switch system as claimed in claim 1 in which the first and second windings havesubs'tantially the same resistance.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 161,739 Bell Apr. 6, 1875 1,635,779 Carter July 12, 1927 FOREIGN PATENTS Number Country Date 261,384 GreatBritain Oct. 6, 1927 562,461

Great Britain July .3,- 1944 

